TWI616641B - Method for measuring wafer thickness using near infrared ray - Google Patents

Abstract

A method for measuring the thickness of a wafer by using near-infrared light. There are two probes above and below the wafer, and a reference plane is virtualized. The upper and lower surfaces of the wafer are not penetrated by near-infrared light. The transmitter of the probe emits near-infrared light, and the reflected near-infrared light is received by the corresponding receiver, and the distance between the farthest distance from the reference plane is calculated to be a first distance, and the closest distance between the reference planes For a second distance. The thickness of the transparent layer is obtained by the difference between the distance between the upper surface or the lower surface of the inner surface and the outer surface thereof and the reference plane, and the second distance is subtracted from the first distance to obtain the transparent layer of the wafer. The total thickness is obtained by subtracting the thickness of the transparent layer from the total thickness to obtain the thickness of the wafer itself, thereby constituting the present invention.

Description

Method for measuring wafer thickness using near infrared ray

The present invention relates to a technique for measuring the thickness of a wafer, and more particularly to a method for measuring the thickness of a wafer using near infrared ray.

According to the invention patent of Patent No. I426574 of the Republic of China, it is disclosed that the optical wave band is irradiated to the semiconductor wafer on the rotary fixing device (6) in a non-contact manner in the direction of the arrow (A) via the measuring head (13) (4) The reflected radiation (16) is transmitted to the spectrometer (17) in the direction of the arrow (B) and analyzed to determine the thickness of the wafer. According to the invention patent of No. 393576 of the Republic of China, the concept of infrared reflection in the two-layer epitaxial wafer shown in Fig. 16(I) is also used to measure the thickness of the wafer. However, if the surface of the wafer of the above two patents is formed with a metal surface during the epitaxial process, in terms of infrared light, since the metal does not have good penetration, only the surface thickness of the metal surface can be measured. The depth of the layer below the metal surface cannot be measured.

According to the new patent case No. M502953 of the Republic of China Patent Publication No. M502953, it is disclosed that the two-wave range finder (41, 42) respectively illuminate the upper and lower sides of the wafer (10), and the reflected wave will be determined by the two-wave range finder (41). 42) Received, applying the relationship between the transmitted wave and the reflected wave, the distance between the second wave range finder (41, 42) and the wafer (10) can be known. Two waves The distance between the distance measuring devices (41, 42) minus the distance between the two reflected waves measured above gives the thickness of the wafer. However, although the measuring device can measure the correct thickness of the wafer, it is known from practical experience that the thickness should be the total thickness. If the wafer contains other layer structures, such as a tape layer or a surface coating layer, It is known from the novel patent how to accurately measure the thickness of the wafer itself.

Therefore, how to solve the above problem of measuring the thickness of the wafer is the focus of the present invention.

The main object of the present invention is to solve the above problems and provide a method for measuring the thickness of a wafer by using near infrared ray, except that the total thickness of the wafer including the transparent layer can be obtained by calculation, and the thickness of the wafer itself can be obtained. It has the accuracy and convenience of measuring wafer thickness.

The wafer is horizontally disposed to have an upper surface and a lower surface, the upper surface and the lower surface are not transparent to near-infrared light, and at least one of the upper surface and the lower surface has a transparent layer. The transparent layer has an inner surface that conforms to the upper surface or the lower surface and has a surface that faces away from the inner surface. For the foregoing purposes, the method of the present invention comprises the steps of: providing a probe: two probes are respectively disposed above and below the wafer, and each of the two probes has a corresponding set of transmitters and receivers. The emitter of the two probes respectively emit near-infrared light to the upper surface and the lower surface of the wafer, and the reflected near-infrared light is received by the corresponding receiver; The reference plane setting: after the two probes are positioned, the two probes themselves virtualize a reference plane on or under the wafer; the measurement: the transmitters of the two probes are respectively on the wafer, The lower surface emits near-infrared light, and the near-infrared light reflected from the upper and lower surfaces is respectively received by the corresponding receiver; the near-infrared light penetrates when the transparent layer is encountered, and the inner surface of the transparent layer The upper surface or the lower surface and the outer surface of the attached surface are reflected by the near-infrared light; the calculation: a computing unit and the two probes are electrically connected to the wafer In the outer surface of the surface and the lower surface and the transparent layer, the distance between the farthest infrared light received by each of the receivers and the farthest distance between the reference planes is calculated as a first distance, and the reference plane The closest distance is a second distance, and the thickness of the transparent layer is obtained by the difference between the upper surface of the inner surface or the lower surface and the outer surface thereof, and the distance between the reference plane and the reference plane, respectively. First distance minus the first It is obtained from the total thickness of the wafer comprising at least one layer of transparent, then subtracting the thickness of the total thickness of the at least one transparent layer of a thickness of the wafer obtained by itself.

Wherein the at least one transparent layer has a layer of tape on a lower surface of the wafer.

Wherein the at least one transparent layer has a protective layer on the upper surface of the wafer.

Wherein, the wavelength of the near-infrared light emitted by the emitter of each of the probes is 850 nm.

Wherein, the total thickness is measured in the range of 50 um to 2000 um.

The above and other objects and advantages of the present invention will be readily understood from

Of course, the invention may be varied on certain components, or in the arrangement of the components, but the selected embodiments are described in detail in the specification and their construction is shown in the drawings.

1‧‧‧ method

11‧‧‧Set the probe

12‧‧‧Base plane setting

13‧‧‧Measure

14‧‧‧ Calculation

2‧‧‧ wafer

21‧‧‧ upper surface

22‧‧‧ Lower surface

3‧‧‧ probe

31‧‧‧transmitter

32‧‧‧ Receiver

4‧‧‧Computation unit

5‧‧‧ Tape layer

51‧‧‧ inner surface

52‧‧‧ outer surface

6‧‧‧Protective layer

61‧‧‧ inner surface

62‧‧‧ outer surface

R‧‧‧ reference plane

D1‧‧‧First distance

D2‧‧‧Second distance

D3‧‧‧ third distance

T‧‧‧ total thickness

T1‧‧‧ thickness

T2‧‧‧ thickness

D1‧‧‧first distance

D2‧‧‧Second distance

D3‧‧‧ third distance

D4‧‧‧fourth distance

T‧‧‧ total thickness

T1‧‧‧ thickness

T2‧‧‧ thickness

T3‧‧‧ thickness

Figure 1 is a flow chart showing the steps of the method of the present invention.

Figure 2 is a state diagram of a preferred embodiment of the present invention with a tape layer on the underside of the wafer and a thickness measured by the two probes.

Figure 3 is a block diagram showing the electrical connection of the two probes and the computing unit of the present invention.

Fig. 4 is a view showing a state in which a tape layer and a protective layer are respectively provided on the lower surface and the upper surface of the wafer, and a thickness measured by the two probes in another preferred embodiment of the present invention.

Referring to Figures 1 through 4, the structure of the embodiment selected for use in the present invention is for illustrative purposes only and is not limited by such structure in the patent application.

The present invention provides a method 1 for measuring the thickness of a wafer using near infrared ray, which is shown in FIG. 1 and includes the steps of providing a probe 11, a reference plane setting 12, a measurement 13 and a calculation 14, wherein:

As shown in FIG. 2, the wafer 2 is horizontally disposed to have an upper surface 21 and a lower surface 22, and the upper surface 21 and the lower surface 22 are not penetrated by near-infrared light, and the upper surface is At least one of 21 and lower surface 22 has a transparent layer having an inner surface that conforms to upper surface 21 or lower surface 22 and has an outer surface that faces away from the inner surface.

Setting up the probe 11: As shown in FIG. 2 and FIG. 3, two probes 3 are respectively disposed above and below the wafer 2, and the two probes 3 each have a corresponding set of transmitters 31 and receivers 32, The emitter 31 of the probe 3 can emit near-infrared light to the upper surface 21 and the lower surface 22 of the wafer 2, respectively, and receive the reflected near-infrared light by the corresponding receiver 32.

Reference Plane Setting 12: As shown in Figures 2 and 4, after the two probes 3 are positioned, the two probes 3 themselves are virtual one bit on the reference plane R on or below the wafer 2.

Measurement 13: As shown in Figures 2 and 4, the emitters 31 of the two probes 3 respectively emit near-infrared light to the upper surface 21 and the lower surface 22 of the wafer 2, and are received by the corresponding receivers 32, respectively. The near-infrared light reflected by the surface 21 and the lower surface 22 is. The near-infrared light penetrates when the transparent layer is encountered, and the upper surface 21 or the lower surface 22 and the outer surface thereof are bonded to the inner surface of the transparent layer, and the reflected near-infrared light is received correspondingly. Received by device 32.

Calculation 14: As shown in FIG. 3, a computing unit 4 and two probes 3 are electrically connected, the upper surface 21 and the lower surface 22 of the wafer 2, and the outer surface of the transparent layer, according to the foregoing receivers 32. The received near-infrared light is calculated to obtain a distance from the farthest distance between the reference planes R as a first distance, and the closest distance between the reference planes R is a second distance, and the thickness of the transparent layer is determined by the distance The difference between the distance between the upper surface 21 or the lower surface 22 and the outer surface of the inner surface and the reference surface R is respectively obtained by subtracting the second distance from the first distance to obtain the wafer 2 including the at least one The total thickness of the transparent layer is further reduced by the thickness of the at least one transparent layer to obtain the thickness of the wafer 2 itself.

Preferably, the wavelength of the near-infrared light emitted by the emitter 31 of each of the probes 3 is 850 nm; moreover, the measurement range of the total thickness is preferably 50 um to 2000 um.

In a preferred embodiment, the at least one transparent layer, as shown in FIG. 2, has a layer of tape 5 on the lower surface 22 of the wafer 2. In this embodiment, in the step of measuring 13, the emitters 31 of the two probes 3 respectively emit near-infrared light to the upper surface 21 and the lower surface 22 of the wafer 2, and are respectively received by the corresponding receivers 32 from above. The near-infrared light reflected by the surface 21 and the lower surface 22 is. When the emitter 31 of the probe 3 below the wafer 2 emits near-infrared light to the lower surface 22 of the wafer 2, the near-infrared light penetrates through the tape layer 5 and is adhered to the inner surface 51 of the tape layer 5 The surface 22 and its outer surface 52, both of which have reflected near-infrared light, are received by the receiver 32 of the probe 3 below the wafer 2.

As a result, in the calculation of the 14 steps, the distance between the upper surface 21 of the wafer 2 and the reference plane R is the farthest distance and is a first distance D1. The outer surface 52 and the reference plane of the tape layer 5 in this embodiment. The distance between R is the closest to a second distance D2, and the surface 22 between the lower surface 51 of the tape layer 5 and the reference plane R is a third distance D3. Here, the thickness T1 of the tape layer 5 is obtained by subtracting the difference between the third distance D3 and the second distance D2, and the second distance D2 is subtracted from the first distance D1 to obtain the total thickness T of the wafer 2 including the tape layer 5, and then The thickness T2 of the wafer 2 itself is obtained by subtracting the thickness T1 of the tape layer 5 from the total thickness T.

In another preferred embodiment, the at least one transparent layer, as shown in FIG. 4, includes the tape layer 5 on the lower surface 22 of the wafer 2, and a protective layer on the upper surface 21 of the wafer 2. 6. The protective layer 6 is a plating film. In this embodiment, in the step of measuring 13, the emitters 31 of the two probes 3 also respectively emit near-infrared light to the upper surface 21 and the lower surface 22 of the wafer 2, and are respectively received by the corresponding receivers 32. The near surface 21 and the lower surface 22 reflect near-infrared light. When the emitter 31 of the probe 3 above the wafer 2 emits near-infrared light to the upper surface 21 of the wafer 2, the near red The external light is penetrated by the protective layer 6, and the upper surface 21 and the outer surface 62 of the inner surface 61 of the protective layer 6 are covered by the receiver of the probe 3 which is reflected by the near-infrared light above the wafer 2. 32 received. When the emitter 31 of the probe 3 below the wafer 2 emits near-infrared light to the lower surface 22 of the wafer 2, it also penetrates the tape layer 5 in the near-infrared light, and is bonded to the inner surface 51 of the tape layer 5. The lower surface 22 and its outer surface 52, both of which have reflected near-infrared light, are received by the receiver 32 of the probe 3 below the wafer 2.

In the calculation step 14, the distance between the outer surface 62 of the protective layer 6 and the reference plane R is the farthest distance of the present embodiment and is a first distance d1. The outer surface 52 and the reference plane of the tape layer 5 in this embodiment. The distance between R is the second distance d2, and the inner surface 51 of the tape layer 5 is a third distance d3 between the surface 22 and the reference plane R. The inner surface 61 of the protective layer 6 is attached. Between the surface 21 and the reference plane R is a fourth distance d4. Here, the thickness t1 of the tape layer 5 is obtained by the difference between the third distance D3 and the second distance D2, and the thickness t2 of the protective layer 6 is obtained by the difference between the first distance d1 and the fourth distance d4, and the first distance d1 is obtained. Subtracting the second distance d2 to obtain the total thickness t of the wafer 2 including the tape layer 5 and the protective layer 6, and subtracting the thickness t1 of the tape layer 5 and the thickness t2 of the protective layer 6 by the total thickness t to obtain the wafer 2 Its thickness is t3.

From the above description, it is not difficult to find that the present invention is advantageous in that even if the wafer 2 is formed into the metal surface as described above on the upper surface 21 or the lower surface 22 during the epitaxial process, the near infrared rays can be disposed by the two probes 3. The light emitter 31 and the receiver 32 are reflected by the near-infrared light emitted by the emitter 31 on the upper surface 21, the lower surface 22 and the outer surface of the transparent layer, and are received by the corresponding receiver 32, and transmitted through the foregoing The calculating unit 4 obtains the distance between each surface and the reference plane R in the calculation step 4, that is, the total thickness of the wafer 2 including the transparent layer is obtained through subtraction, and the The thickness of the wafer 2 itself is obtained by subtracting the thickness of the transparent layer from the total thickness, and the accuracy and convenience of measuring the thickness of the wafer can be achieved.

The above description of the embodiments is intended to be illustrative of the invention and is not intended to limit the scope of the invention.

From the above detailed description, it will be apparent to those skilled in the art that the present invention can achieve the foregoing objects and is in accordance with the provisions of the Patent Law.

Claims (5)

A method for measuring a wafer thickness by using a near-infrared ray, wherein the wafer is horizontally disposed to have an upper surface and a lower surface, the upper surface and the lower surface are not penetrated by near-infrared light, and the upper surface and the upper surface At least one of the lower surfaces has a transparent layer, the transparent layer has an inner surface that conforms to the upper surface or the lower surface, and has an outer surface facing away from the inner surface, the method comprising the steps of: arranging the probe: Two probes are respectively disposed above and below the wafer, and each of the two probes has a corresponding set of transmitters and receivers, and the emitters of the two probes respectively emit the upper surface and the lower surface of the wafer Near-infrared light, and receiving reflected near-infrared light by the corresponding receiver; reference plane setting: after the two probes are positioned, the two probes themselves virtualize a reference plane on or under the wafer; The emitters of the two probes respectively emit near-infrared light on the upper and lower surfaces of the wafer, and the corresponding receivers respectively receive near-infrared light reflected from the upper and lower surfaces; the near-infrared When the light encounters the transparent layer, the upper surface or the lower surface and the outer surface of the inner surface of the transparent layer are covered, and the reflected near-infrared light is received by the corresponding receiver. Calculating: a computing unit and the two probes are electrically connected, and the upper surface and the lower surface of the wafer and the outer surface of the transparent layer are obtained by calculation according to the near-infrared light received by the foregoing receivers. The farthest distance between the reference planes is a first distance, and the closest distance between the reference planes is a second distance, and the thickness of the transparent layer is the upper surface or the lower surface to which the inner surface is attached Obtaining a difference between a distance between the surface and the outer surface thereof and the reference plane, and subtracting the second distance from the first distance to obtain a total thickness of the wafer including the at least one transparent layer, and then subtracting the total thickness The thickness of the at least one transparent layer is obtained to obtain the thickness of the wafer itself. A method for measuring a wafer thickness using near infrared ray according to claim 1, wherein the at least one transparent layer has a tape layer on a lower surface of the wafer. The method of measuring the thickness of a wafer by using near infrared ray according to claim 2, wherein the at least one transparent layer has a protective layer on the upper surface of the wafer. The method for measuring the thickness of a wafer by using near-infrared light according to claim 1, wherein the wavelength of the near-infrared light emitted by the emitter of each of the probes is 850 nm. The method of measuring the thickness of a wafer by using near infrared ray according to claim 1, wherein the total thickness is measured in a range of 50 um to 2000 um.